HP HP-28S User Manual

26
Program Structures
Many programs are equivalent to a series of immediate-execute key-
board computations. Objects go on the stack and commands are
executed, producing the desired result. These programs are simply a
record of
the objects and commands, written in the same order as you
would execute them from the keyboard. However, there are features
you
can use in programs that go beyond simple keystrokes.
For example, in
part 1 you wrote programs that created local vari-
ables.
The special command -t, followed by one or more names,
followed by a procedure, is called a local-variable structure. You can't
execute the command -t from the keyboard; it must appear in the
same program as the names and procedure that constitute the entire
program structure.
This
chapter first reviews the local-variable structure. It then describes
additional program structures that conduct tests and modify program
execution based on the result. All commands for these program struc-
tures
appear in the PROGRAM BRANCH menu. Be sure to read the
first example in "Conditional Structures" on page 223, which intro-
duces concepts used in the remainder of the chapter.
Local-Variable Structure
In part 1 you wrote several user functions, which are the most impor-
tant application of the local-variable structure. There are two
requirements for user functions. They must:
• Explicitly
indicate their arguments .
•
Return exactly one result.
222 26: Program Structures

HP HP-28S Specifications

General

Introduced	1988
Memory	32 KB
Number of Digits	12
Type	Scientific Calculator
Manufacturer	Hewlett-Packard (HP)
Display	LCD
Processor	Saturn
Programming	RPL

Summary

HP-28S Advanced Scientific Calculator Owner's Manual

Part 1: Fundamentals

Introduces basic operations, calculator features, and core concepts.

Getting Started

Covers initial setup, basic operations, and calculator overview.

Doing Arithmetic

Explains methods for performing calculations using stack and expressions.

Part 2: Summary of Calculator Features

Objects

Describes fundamental data types, symbolic operations, and programming elements.

The Command Line

Explains input methods, cursor control, and command entry.

The Stack

Reviews stack concepts and commands for manipulating objects.

Part 3: Programming

Program Structures

Covers conditional logic, loops, and error handling in programs.

Conditional Structures

Explains testing conditions and making decisions within programs.

Definite Loop Structures

Details structures for executing code a specific number of times.

Appendixes & Indexes

Appendix A: Assistance, Batteries, and Service

Provides troubleshooting, battery info, and service details.

Answers to Common Questions

Addresses frequent user queries and common calculator issues.

Appendix B: Notes for HP RPN Calculator Users

Highlights differences for users familiar with RPN calculators.

Appendix D: Menu Map

Lists commands by menu, with descriptions and page references.

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